suboptimal cat usage

To: debian-boot@lists.debian.org
Subject: suboptimal cat usage
From: Philip Hands <phil@hands.com>
Date: Tue, 27 May 2008 14:53:30 +0100
Message-id: <[🔎] 20080527135329.GR8806@hands.com>

Hi,

I thought I'd have a look through the d-i code for instances of:

  cat ... |

to see if I could find any code with room for improvement, and came up
with the attached patch.  Any comments before I commit these?  (along
with relevant changelog entries, of course, and removing the comment
about removing a space from the disk name that's only there to annotate
the patch)

Cheers, Phil.

diff --git a/packages/arch/powerpc/yaboot-installer/debian/postinst b/packages/arch/powerpc/yaboot-installer/debian/postinst
index 0f3d0ed..7a34dd5 100644
--- a/packages/arch/powerpc/yaboot-installer/debian/postinst
+++ b/packages/arch/powerpc/yaboot-installer/debian/postinst
@@ -439,7 +439,7 @@ enablecdboot
 EOF
 
 if [ -s "$extraglobals" ]; then
-    cat "$extraglobals" | writeyabootconf
+    writeyabootconf < "$extraglobals"
     rm -f "$extraglobals"
 fi
 
@@ -477,7 +477,7 @@ EOF
 fi
 
 if [ -s "$extraimages" ]; then
-    cat "$extraimages" | writeyabootconf
+    writeyabootconf < "$extraimages"
     rm -f "$extraimages"
 fi
 
diff --git a/packages/choose-mirror/sort-templates b/packages/choose-mirror/sort-templates
index 32b49d9..9debc93 100755
--- a/packages/choose-mirror/sort-templates
+++ b/packages/choose-mirror/sort-templates
@@ -34,7 +34,7 @@ for template in $templates; do
 
 	for file in list.*; do
 		[ -e "$file" ] || continue
-		[ $(cat "$file" | wc -l) -gt 1 ] || continue
+		[ $(wc -l "$file") -gt 1 ] || continue
 
 		lang=${file#list.}
 		unilang=$(grep "^$lang.* UTF-8" /usr/share/i18n/SUPPORTED | \
diff --git a/packages/debian-installer-utils/chroot-setup.sh b/packages/debian-installer-utils/chroot-setup.sh
index c620ed9..2aa3328 100644
--- a/packages/debian-installer-utils/chroot-setup.sh
+++ b/packages/debian-installer-utils/chroot-setup.sh
@@ -108,9 +108,7 @@ chroot_cleanup () {
 	# Undo the mounts done by the packages during installation.
 	# Reverse sorting to umount the deepest mount points first.
 	# Items with count of 1 are new.
-	for dir in $( (cat /tmp/mount.pre /tmp/mount.pre; mountpoints ) | \
-		     sort -r | uniq -c | grep "^[[:space:]]*1[[:space:]]" | \
-		     sed "s/^[[:space:]]*[0-9][[:space:]]//"); do
+	for dir in $(mountpoints | sort -r /tmp/mount.pre /tmp/mount.pre - | uniq -u); do
 		if ! umount $dir; then
 			logger -t $0 "warning: Unable to umount '$dir'"
 		fi
diff --git a/packages/floppy-retriever/debian/load-floppy.postinst b/packages/floppy-retriever/debian/load-floppy.postinst
index 3d7e1da..6b3e61e 100755
--- a/packages/floppy-retriever/debian/load-floppy.postinst
+++ b/packages/floppy-retriever/debian/load-floppy.postinst
@@ -41,7 +41,8 @@ while true; do
 	label=""
 	mountfloppy
 	if [ -e $FLOPPYMNT/disk.lbl ]; then
-		label=$(cat $FLOPPYMNT/disk.lbl | grep "^Label" | sed "s/Label://")
+		label=$(sed -n "s/^Label: *//p" $FLOPPYMNT/disk.lbl)
+		# N.B. This is a slight modification, in that it eats any space(s) before the disk name -- I'd have thought that's an improvement
 	fi
 	umount $FLOPPYMNT
 
diff --git a/packages/installation-report/report-hw b/packages/installation-report/report-hw
index 5bc69b0..352e72a 100755
--- a/packages/installation-report/report-hw
+++ b/packages/installation-report/report-hw
@@ -10,7 +10,7 @@ addinfo () {
 
 addfile () {
 	if [ -r "$1" ]; then
-		cat "$1" | addinfo "$1"
+		addinfo "$1" < "$1"
 	fi
 }
 
diff --git a/packages/localechooser/get-SUPPORTED b/packages/localechooser/get-SUPPORTED
index 5755cd6..2501bb2 100755
--- a/packages/localechooser/get-SUPPORTED
+++ b/packages/localechooser/get-SUPPORTED
@@ -5,4 +5,4 @@ set -e
 
 [ -r /usr/share/i18n/SUPPORTED ] || exit 1
 rm -rf debian/SUPPORTED-short >/dev/null 2>&1
-cat /usr/share/i18n/SUPPORTED | cut -f1 -d ' ' | uniq >debian/SUPPORTED-short
+cut -f1 -d ' ' /usr/share/i18n/SUPPORTED | uniq >debian/SUPPORTED-short
diff --git a/packages/localechooser/mktemplates.shortlist b/packages/localechooser/mktemplates.shortlist
index da59a44..8280d2f 100755
--- a/packages/localechooser/mktemplates.shortlist
+++ b/packages/localechooser/mktemplates.shortlist
@@ -48,7 +48,7 @@ for LANG in $SHORTLIST_LANGS; do
 
 	# Next we put the countrycodes in the untranslated shortlist
 	SHORTLIST=
-	for COUNTRYCODE in $(cat $SHORTLIST_DIR/$LANG.short | cut -f 1) ; do
+	for COUNTRYCODE in $(cut -f 1 $SHORTLIST_DIR/$LANG.short) ; do
 		SHORTLIST="$SHORTLIST$COUNTRYCODE, "
 	done
 	C_CHOICES=$(echo $EN_CHOICES | sed "s/Choices:/Choices-C:/")
diff --git a/packages/localechooser/sort-templates b/packages/localechooser/sort-templates
index 302e341..d62be2d 100755
--- a/packages/localechooser/sort-templates
+++ b/packages/localechooser/sort-templates
@@ -30,7 +30,7 @@ for template in $templates; do
 
 	for file in list.*; do
 		[ -e "$file" ] || continue
-		[ $(cat "$file" | wc -l) -gt 1 ] || continue
+		[ $(wc -l "$file") -gt 1 ] || continue
 
 		lang=${file#list.}
 		unilang=$(grep "^$lang.* UTF-8" /usr/share/i18n/SUPPORTED | \
diff --git a/packages/partman/partman-basicfilesystems/commit.d/format_basicfilesystems b/packages/partman/partman-basicfilesystems/commit.d/format_basicfilesystems
index 6b7d65e..79a5873 100755
--- a/packages/partman/partman-basicfilesystems/commit.d/format_basicfilesystems
+++ b/packages/partman/partman-basicfilesystems/commit.d/format_basicfilesystems
@@ -77,8 +77,7 @@ for dev in $DEVICES/*; do
 				if [ "$status" = OK ]; then
 					label=''
 					if [ -f $id/label ]; then
-						label=$(cat $id/label | \
-							sed 's/\(................\).*/\1/g')
+						label=$(cut -c-16 $id/label)
 					fi
 					if [ "$label" ]; then
 						log-output -t partman --pass-stdout \
diff --git a/packages/partman/partman-ext2r0/commit.d/format_ext2r0 b/packages/partman/partman-ext2r0/commit.d/format_ext2r0
index 4878821..8321f9f 100755
--- a/packages/partman/partman-ext2r0/commit.d/format_ext2r0
+++ b/packages/partman/partman-ext2r0/commit.d/format_ext2r0
@@ -64,8 +64,7 @@ for dev in $DEVICES/*; do
 			if [ "$status" = OK ]; then
 				label=''
 				if [ -f $id/label ]; then
-					label=$(cat $id/label | \
-						sed 's/\(................\).*/\1/g')
+					label=$(cut -c-16 $id/label)
 				fi
 				if [ "$label" ]; then
 					tune2fs -L "$label" $device
diff --git a/packages/partman/partman-ext3/commit.d/format_ext3 b/packages/partman/partman-ext3/commit.d/format_ext3
index 7bd39b5..e2302b8 100755
--- a/packages/partman/partman-ext3/commit.d/format_ext3
+++ b/packages/partman/partman-ext3/commit.d/format_ext3
@@ -88,8 +88,7 @@ for dev in $DEVICES/*; do
 			if [ "$status" = OK ]; then
 				label=''
 				if [ -f $id/label ]; then
-					label=$(cat $id/label | \
-						sed 's/\(................\).*/\1/g')
+					label=$(cut -c-16 $id/label)
 				fi
 				if [ "$label" ]; then
 					log-output -t partman --pass-stdout \
diff --git a/packages/partman/partman-jfs/commit.d/format_jfs b/packages/partman/partman-jfs/commit.d/format_jfs
index 626ae25..cc73dc4 100755
--- a/packages/partman/partman-jfs/commit.d/format_jfs
+++ b/packages/partman/partman-jfs/commit.d/format_jfs
@@ -59,8 +59,7 @@ for dev in $DEVICES/*; do
 			if [ "$code" = 0 ]; then
 				label=''
 				if [ -f $id/label ]; then
-					label=$(cat $id/label | \
-						sed 's/\(................\).*/\1/g')
+					label=$(cut -c-16 $id/label)
 				fi
 				if [ "$label" ]; then
 					jfs_tune -L "$label" $device
diff --git a/packages/partman/partman-reiserfs/commit.d/format_reiserfs b/packages/partman/partman-reiserfs/commit.d/format_reiserfs
index ce3787a..dbb7f68 100755
--- a/packages/partman/partman-reiserfs/commit.d/format_reiserfs
+++ b/packages/partman/partman-reiserfs/commit.d/format_reiserfs
@@ -62,8 +62,7 @@ for dev in $DEVICES/*; do
 
 				label=''
 				if [ -f $id/label ]; then
-					label=$(cat $id/label | \
-						sed 's/\(................\).*/\1/g')
+					label=$(cut -c-16 $id/label)
 				fi
 				# Ensure label is quoted correctly
 				if log-output -t partman --pass-stdout \
diff --git a/packages/partman/partman-xfs/commit.d/format_xfs b/packages/partman/partman-xfs/commit.d/format_xfs
index 0e3d3bc..cff4c8b 100755
--- a/packages/partman/partman-xfs/commit.d/format_xfs
+++ b/packages/partman/partman-xfs/commit.d/format_xfs
@@ -53,8 +53,7 @@ for dev in $DEVICES/*; do
 
 			label=''
 			if [ -f $id/label ]; then
-				label=$(cat $id/label | \
-					sed 's/\(............\).*/\1/g')
+				label=$(cut -c-12 $id/label)
 			fi
 			code=0
 			# Ensure label is quoted correctly

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